| 摘要 |
PROBLEM TO BE SOLVED: To form a gold plated coating film having excellent adhesion property even to an electroless nickel-boron plated coating film by specifying the concentration of gold ion, the concentration of hydroxy carboxylic acid and the pH of an aq. solution containing a cold compound and a camplexing agent. SOLUTION: The concentration of gold ion is >=0.008 mol/l, preferably 0.01-0.02 mol/l, the concentration of hydroxy carboxylic acid is <=0.01 mol/l, preferably 0.003-0.007 mol/l and the pH is <=6.5, preferably 5-6. The gold compound is a water soluble gold compound such as cyanoaurate, chloroaurate, potassium or ammonium chloroaurate and as the aomplexing agent, hydroxy carboxylic acids, aliphatic carboxylic acids, amino carboxylic acids and amines are preferable in the case of applying the electroless plating on a metallic base material containing nickel. In a process necessary for the electroless nickel- boron plating, a substitutional gold plating is performed without electroless nickel-phosphorus plating.
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